Income Taxes - Valuation Allowance for Deferred Tax Assets (Details) - Valuation allowance for deferred tax assets - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 140.6	$ 67.9	$ 72.5
Revaluation or additions due to acquisitions or mergers	0.0	63.3	0.0
Charged to tax expense	(27.6)	8.3	(5.4)
Charged to other accounts	(6.6)	1.1	0.1
Deductions	0.0	0.0	0.7
Ending balance	$ 106.4	$ 140.6	$ 67.9